Single-fly membrane roofing system

ABSTRACT

A method of applying a roof membrane assembly to a roof deck. The method includes the steps of providing a roof membrane assembly including a first roof membrane and a second roof membrane. The first roof membrane has at least one longitudinally extending edge and the second roof membrane overlaps the first roof membrane and is bonded along at least one longitudinally extending edge of the first roof membrane to define a membrane flap having a longitudinally extending edge. The roof membrane assembly is then positioned upon the roof deck and at least one roof membrane fastening device is positioned over the first roof membrane and beneath the longitudinally extending membrane flap and secured through the first roof membrane and into the roof deck. The longitudinally extending edge of the membrane flap is then bonded to the first roof membrane.

CROSS-REFERENCE TO A RELATED PATENT APPLICATION

This application is a divisional of application Ser. No. 08/706,027filed Aug. 30, 1996 now U.S. Pat. No. 6,004,645, the disclosure of whichis incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to a single-ply membrane roofing system. Moreparticularly, this invention relates to a single-ply membrane roofingsystem having improved resistance to wind uplift forces.

BACKGROUND OF THE INVENTION

A roofing system generally includes a roof deck which is considered thestructural supporting surface of a building extending between thesurrounding exterior walls of the building. The roof deck may beconstructed from plywood, metal decking or concrete or any othersuitable material. Depending upon the construction, the roof deck mayextend over the surrounding exterior walls or the roof deck may stopshort of the exterior walls thereby forming a parapet wall, i.e., a lowretaining wall at the edge of the roof deck. If desired, the roofingsystem may also include an insulation barrier formed frompolyisocyanarate or any other suitable material applied over the roofdeck.

To make the roof deck and building weather resistant a single-plymembrane roof is installed over the roof deck. The single-ply membraneroof refers to a water impermeable single sheet of polymeric materialsuch as ethylene propylene diene rubber (EPDM) having a preapplied hotmelt adhesive, chlorinated polyethylene, polyvinyl chloride, orchlorosulfanated polyethylene. The membrane roof has heretofore beeninstalled on the roof deck using a variety of different methods.

For example, the field or interior of the membrane roof may be held tothe roof deck by the use of ballast and/or penetrating ornon-penetrating fastener means as known in the art. An example of apenetrating fastener means for retaining the field of a membrane roofinstalled to a roof deck is by utilizing a plurality of small, circular,metal plates having a hole in the center and a roofing screw or othersuitable fastener. In order to anchor the membrane roof, the small,circular, metal plates are spaced apart in rows on the membrane roof andthe fastener is driven through the hole in each plate, the membraneroof, any insulation material and then into the roof deck. The metalplates are then covered by overlapping roof membrane. An example of anon-penetrating fastener means would include totally adhering the fieldof the membrane roof to the roof deck.

An important consideration for a mechanically fastened membrane roofsystem is that the system withstand wind uplift forces. Consequently, inorder to withstand wind uplift forces the membrane is typically fastenedto the deck at close intervals over the entire membrane surface therebyminimizing the areas of membrane not secured to the roof deck. If themembrane sheets are secured only along the longitudinal edges the widthof the membrane sheets should be restricted to a dimension of about 5-6feet in order to ensure adequate resistance to uplift in the membranebetween fastening locations.

Although the many known variations for attaching a membrane roof to aroof deck have been proven to perform satisfactorily under certainconditions, further improvements on attaching a membrane roof to a roofdeck are desired.

One object of the present invention is to provide an inexpensivemechanically fastened single-ply roofing system of improved durabilityunder a wide range of climatic conditions and improved resistance towind uplift forces. Yet another object of the present invention is toprovide an improved membrane roofing system which enables transferringto the membrane fabricating plant a substantial amount of the labornormally performed on the roof deck, thereby increasing efficiency andreducing labor costs, as well as assuring reliable product quality byproviding better quality control. Another object of the presentinvention is to provide an improved method of securing a membrane roofto a roof deck in a manner which reduces labor and material costs butwhich does not decrease field performance. It is a further object of thepresent invention to provide an improved method of securing a membraneroof to a roof deck which permits the use of wider sheets of membranethereby minimizing the total number of welded seams of the membranesheets and/or mechanical fastening of the membrane sheets to the roofdeck. Yet another object of the present invention is to provide a methodof installing a membrane roof to a roof deck that is simple andeconomical.

SUMMARY OF THE INVENTION

Briefly, according to this invention, there is provided a method ofapplying a roof membrane assembly to a roof deck. The method includesthe steps of providing a roof membrane assembly including a first roofmembrane and a second roof membrane. The first roof membrane has atleast one longitudinally extending edge and the second roof membraneoverlaps the first roof membrane and is bonded along at least onelongitudinally extending edge of the first roof membrane to define amembrane flap having a longitudinally extending edge. The roof membraneassembly is then positioned upon the roof deck and at least one roofmembrane fastening device is positioned over the first roof membrane andbeneath the longitudinally extending membrane flap and secured throughthe first roof membrane and into the roof deck to secure the roofmembrane assembly to the roof deck. The longitudinally extending edge ofthe membrane flap is then bonded to the first roof membrane such thatthe membrane flap is bonded to the first roof membrane on opposite sidesof the at least one roof fastening device.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and other objects and advantages of this invention willbecome clear from the following detailed description made with referenceto the drawings in which:

FIG. 1 is a sectional view of a roof membrane assembly including a firstroof membrane and a second roof membrane and a membrane flap inaccordance with the present invention;

FIG. 2 is a sectional view of the roof membrane assembly of FIG. 1placed over a roof deck;

FIG. 3 is a sectional view of the roof membrane assembly of FIG. 2mechanically fastened to the roof deck;

FIG. 4 is a sectional view of the roof membrane assembly of FIG. 3 withthe membrane flap secured to the first roof membrane; and

FIG. 5 is a partial top view of a roof deck including a plurality ofroof membrane assemblies.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following description, like reference characters designate likeor corresponding parts.

Referring now to FIG. 1, there is shown a roof membrane assembly 10including a first roof membrane 12 and a second roof membrane 14. Thefirst roof membrane 12 and the second roof membrane 14 refer to waterimpermeable single-ply sheets of polymeric material such asthermoplastic olefins, chlorinated polyethylene, polyvinyl chloride, orchlorosulfanated polyethylene or ethylene propylene diene rubber (EPDM)having a preapplied hot melt adhesive such as a commercially availablepolyester or butyl hot melt and the like. The sheets may be of anysuitable length and width as desired. In a preferred embodiment, eachsheet is about 6 feet wide such that the roof membrane assembly is about12 feet wide. However, it will be appreciated that the width of eachsheet may be as wide as desired subject to manufacturing constraints.

The first roof membrane 12 has at least one longitudinally extendingedge 16. The second roof membrane 14 overlaps the first roof membrane 12and is bonded to the first roof membrane to define a membrane flap 18.In a preferred embodiment, the second roof membrane 14 is bonded alongthe length of the least one longitudinally extending edge 16 of thefirst roof membrane 12. The second roof membrane 14 must overlap thefirst roof membrane 12 sufficiently to provide a membrane flap 18capable of extending and covering over the top of the fastening device20 and capable of bonding to the top surface of the first membrane roof12 on the opposite side of the fastening device as further describedherein. The membrane flap 18 should extend at least about 2.5 inches,and preferably at least about 4 inches from the bond “B” and span thelongitudinal length of the first roof membrane 12 and the second roofmembrane.

The second roof membrane 14 may be bonded to the first roof membrane 12using most any technique well known in the art. For example, the secondroof membrane 14 may be heat welded to the first roof membrane 12 usinga conventional electric heat welder (not shown) which applies heatthrough a single nozzle to the overlapping membranes and compresses themembranes together through a following roller to aid in making a goodbond or weld.

It will be appreciated that it is a feature of the present inventionthat the roof membrane assembly 10 is preassembled from the first roofmembrane 12 and the second roof membrane 14 to simplify fieldinstallation of the roof membrane assembly to a roof deck 22 as furtherdescribed herein thereby allowing for the use of substantially largersheets of roof membrane with no decrease in wind uplift performance.Moreover, it will be appreciated that any number of roof membraneassemblies may be placed in overlapping relation and bonded to form apreassembled continuous membrane thereby further simplifying fieldinstallation.

As shown in FIGS. 2-4, the roof membrane assembly 10 is positioned uponthe roof deck 22. As known in the art, insulation 24 may be applied overthe roof deck 22 as desired. Examples of suitable insulation materialsinclude polyurethane, polystyrene, wood fiberboard, polyisocyanarate andthe like. At a perimeter of the roof deck 22 is a parapet wall 26 whichextends generally perpendicularly upward from the roof deck above theplane of the roof deck. The roof membrane assembly 10 is positioned uponthe roof deck 22 and at least one fastening device 20 is secured throughthe first roof membrane 12 and into the roof deck. It is a feature ofthe present invention that the fastening device 20 is positioned overthe first roof membrane 12 and beneath the longitudinally extendingmembrane flap 18. The fastening device 20 penetrates the first roofmembrane 12 and into the roof deck 22.

The fastening device 20 may include a plurality of conventional threadedfasteners and seam discs for securing the roof membrane to the roofdeck, a plurality of conventional threaded fasteners and one or morebatten bars or, if desired, a suitable combination of the foregoing. Thethreaded fasteners may be conventional screw fasteners of the typecommercially available from Olympic Fasteners, ITW Buildex, SFS Stadlerand Tru-Fast. Similarly, the batten bars and seam discs may also be of aconventional design and of the type commercially available from OlympicFasteners, ITW Buildex, SFS Stadler, Tru-Fast and Talan Products Inc.

As shown in FIGS. 3 and 4, to install the threaded fastener of thefastening device 20, the threaded fastener is inserted into a hole inthe disc or batten bar and through the first roof membrane 12 and intothe roof deck 22 such that the roof membrane assembly 10 is securelyfastened in a fixed position. The threaded fasteners are generallyinstalled in the roof deck 22 at a spacing ranging from approximatelyevery 6 inches to every 16 inches depending upon the wind uplift forcesexperienced by the roof membrane assembly. Under typical conditions, thepreferred fastening device 20 spacing is about every 12 inchesregardless of the fastening device used.

The longitudinal edge of the membrane flap 18 is then bonded to thefirst roof membrane 12 such that the membrane flap is attached to thefirst roof membrane on both sides of the fastening device 20. Thelongitudinally extending edge of the membrane flap 18 is bonded to thefirst roof membrane 12 using any suitable technique well known in theart. In a preferred embodiment, the membrane flap 18 is heat welded tothe first roof membrane 12 as previously described. It will beappreciated that the membrane flap 18 protects the fastening device 20from the elements such that water proofing of the fastening device isnot required. In addition, the resulting “double seam” bond “B” on eachside of the fastening device 20 provides increased wind upliftresistance such that the spacing between rows of fastening devices maybe increased with no decrease in wind uplift performance (see FIG. 5).Moreover, by prefabricating the membrane roof assembly with a membraneflap 18, the properties of a “dual weld” membrane roof such as describedin U.S. Pat. No. 4,834,828 may be achieved by simple application of asingle weld after installation of the membrane roof assembly 10 inaccordance with the present invention as opposed to simultaneous fieldapplication of a dual weld.

As shown in FIG. 5, a plurality of membrane roof assemblies 10 aresecured to a roof deck 22. The roof membrane assemblies 10 are placed inan overlapping relation “O” and bonded together as well known in theart. The overlapping regions of roof membrane assemblies 10 may includeadditional fastening devices 20 as desired.

It will be appreciated that because the distance between fasteningdevices 20 can be substantially increased over distances typically usedin the past, the time and labor typically required for the installationof the fastening devices is greatly reduced, and since this is a manualon site operation, a large amount of the installation cost is saved.

The invention will be further clarified by a consideration of thefollowing example, which is intended to be purely exemplary of theinvention.

EXAMPLE 1

A heat weld system as shown in FIG. 4 was welded on each side of amechanical fastener and tested in accordance with Factory Mutual winduplift testing procedures as well known in the art. The heat weld systemwas tested in a 12 foot by 24 foot chamber having a steel deck on thetop surface. The roof system was applied over insulation to the steeldeck. The roof system was then pressurized over time from underneath at15 psf intervals starting at 30 psf. The roof system was held at eachinterval for 1 minute and then increased until the roof system failed.

With a single weld and number 14 screws at 6 inch on-center spacing a1-90 rating was achieved. However, with the double weld roof system inaccordance with the present invention using number 14 screws at 6 inchon-center spacing a 1-120 rating was achieved.

It is believed that the reason for improved wind uplift resistance wasthat the roof system was loaded in shear rather than in peel where thevalues are typically 3-4 times greater. Moreover, the mechanicalfastener pulled up straight rather than at an oblique angle aspreviously experienced which maximized the pull out value of thefastener from the roof deck.

It will be appreciated that there are additional advantages to a doubleweld system in accordance with the present invention. For example, weldsthat are only tacked together but are not completely fused are known ascold welds and can drop in peel strength down to a psi—20 psi thesevalues in shear are still 40 psi-60 psi which eliminates many of thequality issues on the roof.

There are also advantages in testing where the system is being cycled.If the roof does not fail from the first wind storm, irreversible damagecan occur in a single weld roof system especially where barbed platesare used. This can create tearing of the membrane and make it easier tofail in subsequent storms. It is much more difficult to createirreversible damage to a double welded system because the wind upliftforces experienced are pulling straight up on the top of the membranewith no tearing action.

The documents, patents and patent applications referred to herein arehereby incorporated by reference.

Having described presently preferred embodiments of the invention, it isto be understood that it may be otherwise embodied within the scope ofthe appended claims.

What is claimed is:
 1. A method of applying a roof membrane assembly toa roof deck to cover the roof deck comprising the steps of: providing aroof membrane assembly including a first roof membrane and a second roofmembrane, said first roof membrane having at least one longitudinallyextending edge, said second roof membrane overlapping said first roofmembrane and bonded to at least one longitudinally extending edge ofsaid first roof membrane to define a membrane flap having alongitudinally extending edge, positioning the roof membrane assemblyupon the roof deck; positioning at least one roof membrane fasteningdevice over said first roof membrane and beneath said longitudinallyextending membrane flap; securing said at least one roof membranefastening device through said first roof membrane and into the roof deckto secure said roof membrane assembly to the roof deck; and then bondingsaid longitudinally extending edge of said membrane flap to said firstroof membrane such that said membrane flap is bonded to said first roofmembrane on opposite sides of said at least one roof fastening devicethereby providing a dual bond joining said first and second membranewherein a portion of the first roof membrane and a portion of the secondroof membrane [are contiguous] contacts the surface of the roof deck onopposite sides of the dual bond.
 2. The method of claim 1 wherein thefirst roof membrane and the second roof membrane are water impermeablesingle-ply sheets of polymeric material.
 3. The method of claim 1wherein the first roof membrane and the second roof membrane are waterimpermeable single-ply sheets of polyvinyl chloride.
 4. The method ofclaim 1 wherein the membrane flap extends at least about 2.5 inches fromthe bond to said first roof membrane and spans the longitudinal lengthof said first roof membrane and said second roof membrane.
 5. The methodof claim 4 wherein said second roof membrane is bonded to said firstroof membrane by heat welding.
 6. The method of claim 1 wherein said atleast one fastening device is at least one threaded fastener and atleast one seam disc.
 7. The method of claim 1 wherein said at least onefastening device is at least one threaded fastener and at least onebatten bar.
 8. The method of claim 1 wherein said at least one fasteningdevice are installed in the roof deck at a spacing ranging between about6-16 inches.
 9. The method of claim 1 wherein said longitudinal edge ofsaid membrane flap is heat welded to said first roof membrane such thatsaid membrane flap is bonded to said first roof membrane on both sidesof said at least one fastening device.
 10. The method of claim 1 furthercomprising the steps of: providing a plurality of membrane roofassemblies to said roof deck in overlapping relation; and bonding saidoverlapping relation.
 11. A method of applying a roof membrane assemblyto a roof deck comprising the steps of: providing a roof membraneassembly including a single-ply first roof membrane and a single-plysecond roof membrane, said second roof membrane overlapping said firstroof membrane and welded to said first roof membrane to define amembrane flap; positioning the roof membrane assembly upon the roofdeck; positioning at least one roof membrane fastening device over saidfirst roof membrane and beneath said membrane flap; securing said atleast one roof membrane fastening device through said first roofmembrane and into the roof deck to secure said roof membrane assembly tothe roof deck; and then heat welding said membrane flap to said firstroof membrane such that said membrane flap is welded to said first roofmembrane on opposite sides of said at least one roof fastening device toprovide a dual bond joining said first and second membrane such that aportion of the first roof membrane and a portion of the second roofmembrane contacts the surface of the roof deck on opposite sides of thedual bond.
 12. The method of claim 11 wherein said at least onefastening device is at least one threaded fastener and at least one seamdisc.
 13. The method of claim 11 wherein said at least one fasteningdevice is at least one threaded fastener and at least one batten bar.